Polaroscope



Q. A. KERNS POLAROSCOPE June 1, 1954 9 sheets-sheet 1 Filed June 19,1947 A Trop/VE? Q. A. KERNS` June 1, l 954 POLAROSCOPE 9 Sheets-Sheet 2Filed June 19. 1947 June l, 1954 Q A, KERNS 2,680,227 L PoLARoscoPEFiled June 19, 1947 9 Sheets-Sheet 5 \1 \1 \I \I r if i 1: z L

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VOL 75465 OUTPUT OF OUTPUT C/PCU/T 64 /M/ENTOR QUE/VHN A. KER/vs ATTOR/I/Ey Q. A. KERNS June 1, 1954 POLAROSCOPE 9 Sheets-Sheet 4 FiledJune 19, 194'7 A Tram/EY Q. A. KERNS June l, 1954 POLAROSCOPE 9Sheets-Sheet 5 Filed June 19. 1947 QuE/WWA AE/eA/S from/5y Q. A. KERNSPOLAROSCOPE June 1, 1954 Filed June 19, 1947 9 Sheets-Sheet 6 SOON lArm/wey Q. A. KERNS POLAROSCOPE June 1, 1954 9 Sheets-Sheet 7 Filed June19. 1947 u I IIIIII; oww wm" www NQN mww/ n \mN @NN was@ Arrow/6V Q. A.KERNS POLAROSCOPE June l, 1954 9 Sheets-Sheet 8 Filed June 19. 1947QUA/r/A/ A, Kem/5 mam /l Wow/ey Q. A. KERNS `lune l, 1954 POLAROSCOPE 9Sheets-Sheet 9 Filed June 19, 1947 A T rom/EV Patented June 1, 1954PoLARosooPE Quentin A. Kerns, Berkeley, Calif., assigner to the UnitedStates of America as represented by the United States Atomic EnergyCommission Application June 19, 1947, Serial No. 755,794

2 Claims., (Cl. 324-31) This invention relates to a polaroscope and moreparticularly to an apparatus for the electro-chemical analysis of liquidsolutions.

In polarographic analyses of liquid electrolytes as developed todetermined the reducible components in the electrolytes, use is made ofan electrolytic cell having a dropping mercury capillary tube as oneelectrode and a mercury pool as the other electrode, both electrodesbeing immersed within the electrolyte to be analyzed.

To analyze the electrolyte a varying voltage is applied between the twoelectrodes of the cell and a study made of the resulting current-voltagerelation. This study reveals a stepped current variation with respect tovoltage changes; the voltage at which each current step occurs is thecharacteristic deposition voltage for a particular reducible componentof the electrolyte and the height of each current step is proportionalto the quantity of that particular reducible component. In practice thecurrent-voltage relation is recorded on a moving graph and suchv a graphis known as a polarogram. Further, a method has been devised whereby thecurrent voltage relation is portrayed on an oscilloscope; L

however, the apparatus involved is quite simple and does not include acontroller circuit for automatically and correctly applying the varyingvoltage at predetermined intervals during the formation of the mercurydrops.

In order to obtain a more rapid visual analysis it is proposed by thisinvention to record the current-voltage characteristic curveinstantaneously on the screen of a cathode ray tube. In order that thecurves so obtained are accurate and consistent, it is necessarythat aperiodically varying voltage of sawtooth wave form be applied to thedropping mercury cell at a predetermined time during the formation of amercury drop. That is, it is `desirable that the varying voltage beapplied when the drop has almost reached its maximum size, when its rateof growth is relatively small, when its size is substantially the sameas previous drops, and just prior to the drop breaking off and fallingfrom the tip of the capillary tube electrode. To initiate the generationof this varying voltage of sawtooth Wave form and to apply it at theproper interval in the development of a mercury drop, a rather complexcontrol circuit has been devised. This control circuit or controller, asit is known, provides the necessary timing for a complete cycle ofoperation which occurs in the period between the instants of breakingofi' of successive mercury drops, namely:

sawtooth wave of voltage returns to minimumv value and ends when lthedrop falls from the tip of the capillary electrode and another dropbegins to form, thus completing the cycle of operation.

To obtain the current-voltage curve on the v screen of the cathode raytube, three amplifiers are employed. The principal amplifier is of thenegative feedback type having a large feedback resistance and a highvalue of round trip trans-V mission coeicient. 'Ihe varying Voltage ofsawtooth waveform is applied to this negative feedback ampliiier and tothe dropping mercury cell which is connected to the feedback networkbetween the amplifier input and ground. With such an arrangement, thevoltage across the cell is proportional to and can be made almost equalto the amplier input voltage and the voltagedrop in the feedbackresistance is proportionalV to the cell current.4 Through the medium ofthe negative feedback circuit, even though the effective resistance ofthe cell varies with the volt-v age across the cell, the sawtoothvoltage wave of the desired magnitude and form is always impressed onthe cell and a voltage drop proportion al to thev cell current isobtained across the feedback resistance. The varying voltage of sawtoothwaveform applied to the negative feedback sam--v plifler as Vdescribedis also applied to the input of a4 conventional oscilloscope typeamplier, the

output of which is connected to the horizontal deiiecting plates of thecathode ray tube. The vertical deflecting plates of said cathode raytube are supplied with a voltage obtained from another oscilloscope typeamplifier having its input ycircuit connected to the feedback amplieroutput so that the voltage thus impressed across' said verticaldeflecting plates is proportional to the cell current.

It is therefore an object of this invention to provide a new andimproved apparatus for electrochemical analysis of electrolyticsolutions.

A further object of this invention is to provide a new and improvedapparatus for electrochemical analysis of electrolytic solutions whichautomatically produces a visual polarogram during a predeterminedfraction of the interval between birth of a new mercury drop and of thebreaking off of said drop at the tip of a capillary electrode.

Another object of thisy invention is to provide a new and improvedapparatus for electrochemical analysis of electrolytic solutions whichautomatically produces a linearly varying voltage across an electrolyticsolution at a predetermined time during the formation of a mercury dropso that said linearly varying voltage is applied at the same instant foreach drop to eliminate errors due to changes in mercury drop size forsuccessive polarograms.

Still another object of this invention is to provide a new and improvedapparatus for electrochemical analysis of electrolytic solutions whichautomatically produces a voltage of rectangular wave form simultaneouswith the generation of a linearly varying voltage, which. deflects theelectron stream of the cathode ray tube away from the screen exceptduring the interval when said linearly varying voltage is applied to theelectrolytic solutions, thereby preventing spurious traces on the screenof said cathode ray tube.

A still further object is to provide a new and v improved apparatus forelectrochemical analysis of electrolytic solutions which automaticallyproduces a voltage proportional to the current which flows through anelectrolytic solution when a linearly varying voltage is impressedacross said electrolytic solution so that said proportional voltage canbe utilized in the visual analysis of said electrolytic solution on thescreen of a cathode ray tube.

Other objects and advantages of the invention will be apparent in thefollowing description and claims considered together with theaccompanying drawing in which:

Figure 1 is a schematic block diagram oi the polaroscope showing theinterconnections of signal voltages between the components;

Fig. 2 is a schematic block diagram of the polaroscope showinginterconnections of direct current operating voltages between the powersupply and the other components;

Fig. 3 is a series of time correlated graphs showing the subsequence ofwave forms involved in the operations occurring in various parts of thepolaroscope circuit; y

Fig. 4 is a schematic wiring diagram of the negative feedback amplifierand the dropping mercury cellrcomponents of the polaroscope;

Fig. 5 is aschematic wiring diagram of the initiator componentcomprising a derivator circuit, a drop detector circuit, an impulsegenerator circuit, and a dropping rate meter circuit;

Fig. 6 is a schematic wiring diagram of the voltage generator componentcomprising a sawtooth wave generator circuit and an output circuit;

Fig. *7 is a schematic wiring diagram of the timer component comprisingtwo trigger circuits;

Fig. 8 is a schematic wiring diagram of the balanced amplifier componentand the cathode ray tube component; and

Fig. 9 is a schematic wiring diagram of the reproducing ampliercomponent of the polaroscope.

Now referring to the drawings in detail, and in particular to Fig. 1,the polaroscope comprises a negative feedback amplier component i0, a

dropping mercury cell component 20, a balanced amplier component 30, areproducing amplifier component 40, a cathode ray tube component 50, anda controller component 50. Said controller component 50 has severalsub-components, namely: an initiator 'it comprising a derivator circuit12, a drop detector circuit 14, an impulse generator circuit T6, and adropping rate meter circuit 18; a voltage generator Si! comprising asawtooth generator circuit 82 and an output circuit 84; a timercomprising a trigger circuit 82 and a trigger circuit 94; and a powersupply |00. The interconnections between the components and circuitswill be. explained in detail hereinafter in the description of the otheriigures of the polaroscope.

Fig. 2 represents the distribution of direct current static operatingvoltages between the power supply |00 and the other components andcircuits oi the polaroscope. The power supply E00 is a conventionalrectifier type, with an alternating current input, toY supply staticoperating voltages of 1000, 200, 150, and +280 volts plus a common leadat ground potential for the vacuum tubes in the polaroscope circuit.

Fig. 3 represents a series of time correlated graphs showing thesubsequence of current and voltage waveforms during the intervals ofoperation of the polaroscope. A sawtooth waveform IBS is the form oi thevoltage impressed across the dropping mercury cell 28. A steppedwaveform 102 is the form of the current flowing through the droppingmercury cell 2li during the time that the voltage of waveform Nil isimpressed across said dropping mercury cell 20. A waveform |03, similarto the waveform 102, is the voltage output of the negative feedbackamplier l0. The waveform |234 is the waveshape of the voltage output ofthe derivator l2. The pulse waveform |05 is the waveshape of the voltageoutput of the drop detector 74. The rectangular waveform 05 is the formof the output voltage of the trigger circuit 94. The pulse waveshape i'lis similar to the voltage waveshape l 05 of the drop detector lf3 and isthe waveshape of the output voltage of the impulse generator lt. Thesawtooth waveform IES is the waveshape of the output voltage of thesawtooth generator 82. The rectangular 'waveform l09 is the waveshape ofthe output voltage of the trigger circuit 92. The sawtooth waveform H0is the waveshape of the output voltage of the output circuit 84. Furtherreference will be made to said current and voltage waveforms hereinafterin the description of the other figures of the polaroscope.

In Fig. '4 a negative feedback amplifier Ii! comprising three pentodevacuum tubes, i l i, H2 and H3, which give three stages ofampliiication, and.

a pentode tube I I4 which acts as a coupling tube is shown. An inputlead HB is connected to the control grid of said coupling tube 1M and'supplies aV voltage of waveform i0! as shown on Fig. 3. Otherconnections of said tube l I4 are as fol'- lows: the plate is connectedto the +280 volt direct current source through a dropping resistor Illand to ground through a by-pass condenser H3; the screen grid isconnected to the screen grid of the pentode IH, to the +280 volt directcurrent source through a dropping resistor HS, and to ground through aby-pass condenser i201 the cathode is connected to the cathode of saidtube Hl through a cathode bias resistor |24 and to the 150 volt directcurrent source through a dropping resistor 122. The plate of saidpentocle tube is connected to the +280 volt direct current sourcethrough a dropping resistor |23' and further to the control grid of thesecond' amplifying pentode tube I2 through a 'coupling network |24comprising a capacitor |25 connected in parallel with a resistor |26.Further connections of said tube II2 are as follows: the control grid isconnected to a voltage divider through a dropping resistor |21 by meansof the adjustable arm of a potentiometer |28 which combined with aresistor |29 forms a source of variable biasing voltage, serving as thezero adjustment for the circuit between ground and the 150 volt directcurrent source, and further to a lead' I3 I, through a resistor |32,which supplies a voltage of rectangular waveform |06 as shown on Fig. 3;the screen grid is connected to the +150 volt direct current source; thecathode is connected to ground through a biasing resistor |34; the plateis connected to the +`80 volt direct current source through a droppingresistor |35, and further to the control grid of the third pentodeamplifier tube I I3 through a coupling network |36 comprising acondenser |31 connected in parallel with a resistor |38. Furtherconnections of saidl tube |I3 are as follows: the control grid isconnected to the -150 volt direct current source through a droppingresistor |39; the cathode is connected to ground; the screen grid isconnected to the +150 volt direct current source; the plate is connectedto the +280 volt direct current source through a dropping resistor |49,and further to a coupling network 4| comprising a condenser |42connected in parallel with a neon bulb |43. Said ycoupling network I4Iis connected to an output lead |44 which furnishes a voltage of waveform|93 as shown on Fig. 3 to other components of the polaroscope, andfurther to a dropping resistor |45 which is connected to the -200 voltdirect current source. The voltage at said output lead |44 is impressedon the cathode of said tube ||2 through a coupling network |46comprising a condenser |41 connected iur-parallel with a resistor I 48,and on the control grid of said tube I I I through a variable couplingnetwork |49 comprising a condenser I5I connected in parallel with one ofseveral resistors |52, |53, |54, |56, |51, |58, |59, |6| or |62 asselected by switch |63. Said coupling network |49 is connected to a lead|64 which is connected through a plug |65 to the mercury pool |66 of thedropping mercury cell 2U. The mercury' reservoir of the capillaryelectrode |51 of said cell 23 is connected to ground. Y

With the elements and interconnections as de` scribed in the precedingparagraph, said Fig. 4 represents a negativefe'edback amplifier ll!circuit with a dropping mercury cell connected across the feedbackvoltage. The coupling tube |4is included in the rst of three stages ofarnplication to facilitate the application of a voltage of sawtoothwaveform to said amplifier I0 with the least amount `of distortion andVunbalance. It is further necessary that said coupling tube I| 4 and thepentode amplifier tubeII of the first stage of amplification be of thesame type and have a common screen grid..voltage supply circuit. Aby-pass condenser |I8 is connected between the plate of said couplingtube I I4 and ground so that voltage variations at said plate aregrounded and do not affect the tube operation. Therefore, during thesecond interval of operation when a positive sawtooth wave of voltage isapplied at the control grid of the coupling tube II4, the currentflowing through said tube |I4 increases. thereby causing an ln-phasvoltage change of the same waveform to appear low impedance for thevarying voltage. The nor` mal control grid bias for said tube II2 may beadjusted by the potentiometer |28. IIg'hus, the voltage at the controlgrid of said tube'II2 increases causing the current flowing through thetube to increase, thereby decreasing the plate voltage in a similarmanner, so that'there is-a sawtooth voltage change of oppositepolarityat said plate. There is also present in this second stage ofamplification a small amount of degen'erv ative action because of theself-biasing cathode resistor |34; that is, as the current through the'tube I2 increases, the voltage across said resistor |34 increases andtends to raise the potential at the cathode, thereby opposing by a smallamount the tube action due to the voltage applied at the'control grid.

Said sawtooth voltage change of opposite polarity at the plate of saidtube |I2 is impressed on the control grid of the third pentode amplifiertube 3 through the low impedance coupling network I 36 and across theresistor |39 and causes the current flow through the tube to decreasethus increasing the plate voltage rso that a positive sawtooth wave ofVoltage is present at the plate.

The output voltage of the amplifier I0 is taken from the plate of saidtube II3 by the lead |44 through the coupling network I4I. A portion ofthe output voltage is fed back to thesecond amplifier stage through thecoupling network |46 and is applied across the resistor |34 in thecath-y ode circuit of the tube I I2. Since said output voltage is apositive sawtooth wave of voltage, the potential at the cathode risesandcauses .a decrease of the current iiowing in the tube, thus opposingthe tube action in response to the signal applied at the control grid.

Also, a portion of said output voltage is fed back to the control grid'of the tube of the first amplifier stage through a coupling network |49.Said coupling network |49 comprises `thecondenser I5I, the plurality ofresistors |52, |53, |54, |56, |51, |58, |59, ISI and |62, and theselector switch |53; thus by using said selector switch the impedance ofthis coupling networkmaybe changed according to the value of resistanceselected, thereby manually controlling the amount of voltage which isfed back to the first stage of amplification. Since the overall gain ofa feedback amplifier system such as has been outlined above isproportional to the amount of voltage which is actually fed back fromthe output to` the input, the overall gain of the amplifier |6- may bemanually controlled by changing the position of said selector switch|53.

With the dropping mercury cell 29, in position y as shown on said Fig.4, that is, connected between -the control grid of the ilrst amplifierstage 7T. the second interval of operation the voltage is of sawtoothWaveform.

During the third interval of operation of the polaroscope a positivevoltage of rectangular waveform |06 as shown on Fig. 3 is impressed onthe control grid of the second amplifier tube I|2. Said positiverectangular Wave of voltage is ampliiled in the second and third stagesof ampli-l fication and is negatively fed back in the same manner as-thesawtooth Wave of voltage during thel second interval of operation asdescribed above. In the rst interval there are no voltages applied vtothe negative feedback amplifier I sothat said amplier- I0 is in aquiescent state. Therefore, the voltage across the dropping mercury cellduring one cycle of operation of the polaroscope is of the waveshape |0|as shown on F'. 3, s

In the second interval of the cycle of operation a sawtooth wave ofvoltage is impressed across the dropping mercury cell 20 as a newmercury drop is forming on the tip of the drop-` ping mercury electrode61. The resistance of the electrolyte between the dropping mercuryelectrode '|81 and the mercury pool IBS decreases eachV time thedeposition voltage of a reducible component in said electrolyte isreached causing a stepped current of waveform |02 as shown on Fig. 3.Because of the resistance in the coupling network |09 of the feedbackcircuit the voltage applied across the dropping mercury cell 20 remainsin the form of waveshape EBI as shown on Fig. 3 and the voltage acrosssaid resistance in the coupling network |49 will be proportional to thecurrent flowing in said cell 20 and in the form of waveshape |03 as.shown on Fig. 3. Therefore, the changes in the feedback voltage causedby changes in the resistance of the dropping mercury cell 20 areamplified through the three amplifier stages of the negative feedbackarnplifier so that the output voltage is proportional to the sum of theinput voltage .and the voltage drop across the resistance in thefeedback coupling network U59 and is of the form of waveshape |93 asshown on Fig. 3.

Since during the third interval of operation a positive voltage ofrectangular waveform |06 is applied to the second aniplier stage, thisvoltage also is applied across the dropping mercury cell 20. At the timethe droprfalls from the tip of the dropping mercury electrode, theresist-ance of the cell 20 increases by a large amount causing theefective gain of the negative feedback amplifier to decrease and thuscausing the voltage appearing at the output to. decrease.

Now considering Fig. lead |44. furnishes a voltage of raveiorin 03 asshown on Fig. 3 to the deriva-tor circuit 12 of thev initiator component10 and is connected toV a condenser 15S which is connected to groundthrough a resistor |09 and to a lead |11.

Said lead Ill is connected to the control grid of a'pentode tube |12 andfurnishes a voltage input of Waveform I0@ to the drop detector circuit14. Other connections of said tube |12 are as follows: the cathode isgrounded, the screen grid is connected to the +280 volt direct currentsource through a dropping resistor |13 and to ground through a by-passcondenser lill, and the plate is connected to a resistor |15 and to alead |10. Said resistor |15 is connected to ground through a by-passcondenser |11 and to a resistor |10. Said resistor Vic is connected tothe lead 13| which supplies a voltage of Waveform |00 as shown on Fig.3, and to a potentiometer |19 8. which is connected to ground and servesas a drop rate adjustment. The adjustable arm of said potentiometer |19is connected to a resistor which is connected to a potentiometer |8|which may be adjusted to control the value of the sawtooth waveform II0. Said potentiometer I'l is connected to ground and its adjustable armis connected to the lead I IB which supplies a Voltage of Waveform |0|as shown on Fig. 3 to the negative feedback ampliiier I0. A resistor |82is connected to a lead |83 which supplies a voltage of waveform ||0 asshown on Fig. 3 across said resistor |82 and potentiometer |3I.

Said lead |10 couples a voltage of waveform |05 as shown on Fig. 3, fromthe plate of said tube |12 to the control grid of triode B of a doubletrode tube |89 through a coupling condenser |90 in the impulse generatorcircuit 16. Other connections of said triode B of the tube 89 are asfollows: the cathode is connected to ground; the control grid isconnected to a dropping resistor |9| which is connected to ground,` to aresistor |92 which is connected to the -150 volt direct current source,and further to the plateof tricde A of a double triode |93 through acoupling network comprising a resistor |94 in series with a variablecondenser |96; the plate is connected to the +280 volt direct currentsource through a dropping resistor $01, and to the control grid of saidtriode A of tube |93 through a coupling condenser |98. Furtherconnections of said triode A of tube |93 are as follows: the controlgrid is connected to ground through a grid biasing resistor |99 and to alead 20| which furnishes a negative pulse at the start of the firstinterval of operation to other components of the polaroscope, the plateis connected to the +230 volt direct current source through a droppingresistor 202, and the cathode is connected to the volt direct currentsource through a dropping resistor 203, and to a iead 204.

Said lead 204 is connected to the cathode of section B of said tube |93and furnishes a voltage of waveform |01 as shown on Fig. 3 to thedropping rate meter 18. The control grid and plate of said section B ofthe double triode tube |93 are connected together and further connectedto the control grid of a pentode tube 20,6. Other connections of saidtube 206 are as follows: the cathode is connected to ground, the

screen grid is connected to the +150 volt direct current source, and theplate is connected to a neon bulb 201 and a condenser 200. Said lamp 201is further connected to the -200 volt direct current source through adropping resistorl 2|0 and to the control grid of triode A of a doubletriode tube 2|| through a resistor 2|2. Said condenser 208 is alsoconnected to the control gridvof triode A of said tube 2H. Otherconnections of triode A of said tube` 2H are as follows: the plate isconnected to the +230 volt direct current source and the cathode isconnected to the -150 volt direct current source through a .biasingresistor 2|3 and further to a lead 2|4. Said lead 2M is connected to thecontrol grid of said pentode tube 206 through a coupling network 2I5comprising a resistor 2| 6 connected in parallel with a condenser 2|1.

Consider now the operation of the initiator i 10 circuits which aredescribed above. The derivator is a simple condenser-resistor type ofcircuit and operates to provide an output voltage which is proportionalto the rate of change of the input voltage. Since the lead |44 applies avoltage of waveform |03 to said derivator 12, the

9 output voltage is a series of pulses and has a Waveform |04 as shownon Fig. 3.

The output voltage of the derivator 12 is impressed on the controlgridof a pentode amplifier tube |12 inthe drop detector 14 circuit. The lead|3| applies a positive voltage of rectangular Waveform |06 as shown onFig. 3, the value of which is adjustable by the potentiometer |19 to theplate of said tube |12 so that the tube will pass voltages appearing atthe control grid only during the third interval or operation. Thus, theoutput voltage of the drop detector is a positive pulse occurring as thethird interval ter- Inmates.

Said positive pulse of voltage appearing at the plate of tube |12 in thedrop detector 14 circuit is applied to the control grid of triode B ofthe double triode tube |89 in the impulse generator 16 which comprisessaid triode B of the tube 89 and the triode A ci' the double triode tube|93 interconnected in the form of a conventional self-restoring triggercircuit. Said triode B of the tube |89 is normally biased to cut-off bythe negative biasing voltage while triode A of said tube |93 normally isconducting since the control grid is at ground potential. The positivepulse impressed at the control grid of said triode B of the tube |89causes current to ilow in the tube and this current causes a voltage tobe developed across the plate dropping resistor |91 which decreases thevoltage at said plate. This decrease in plate voltage of triode B ofsaid tube |89 is coupled to the control grid of triode A of the tube 93through the condenser |98 so that the latter tube is cut-olf causing theplate voltage to increase and the cathode Voltage to decrease. Theincrease of plate voltage of triode A of said tube |93 is coupled to the'control grid of triode B of said tube |89 through the variablecondenser |96 and resistor |94. Said variable condenser |96 may beadjusted so that the time constant of the condenser |96 and theresistors |94 and |9| of the discharge path of said condenser |96 is asmall value so the output voltage of the impulse generator 16 circuitwill follow theinput pulse of voltage. This entire action isinstantaneous and the two referenced tubes return to the normal state assoon as the positive pulse of voltage on the control grid of triode B ofsaid tube |89 has fallen to zero value. Negative pulses of voltage atthe control grid of triode A of said tube |93 are connected to anothercircuit of the controller 60 by the lead 20|. NegativeV pulses ofVoltage at the cathode of triode A of said tube |93 are applied to thedropping rate meter by means of the lead 204. Thus the impulse generator16 produces successive negative pulses of constant magnitude at a rateequal to the dropping rate of the mercury drops in the dropping mercurycell 20.

Said lead 204 impresses the negative pulse output voltage of waveform|01, as shown on Eig. 3, of the impulse generator 16 circuit on thecathode of triode B of the double triode tube |93 in the dropping ratemeter 18 circuit. Since said triode B of the tube |93 is connected sothat the plate and control grid are tied together, the tube functions asa diode tube and passes signal voltages only when such signal voltagesare negative. The pentode tube 206 and the triode A of the double triodetube 2|| form two stages of a negative feedback amplier circuit with acoupling network 2|5 for connecting the output voltage in the cathodecircuit of said triode A of the tube 2|| tothe control gridof saidpentode 75 tube 206. 'I'he negative pulse of Voltage which is impressedon the cathode'of said triode B of the tube |93 causes this tube toconduct, since the cathode becomes more negative than the anode, and thecurrent flow produces a voltage proportional to the dropping rate acrosssaid coupling network 2|5. The voltage across said coupling network 2I5is amplified through the two amplifier stages comprising the pentodetube 206 and triode A of the double triode tube 25| and finally fed backnegatively through said coupling network 2 l5 to the control grid ofsaid pentode tube 206. The circuit elements are of such values that theapparent input impedance f of the amplifier circuit comprises airesistance reduced in value by the amplification factor and acapacitance increased in value by the amplification factor connected inparallel having the same time constant as the resistor 2|6 and thecondenser 2|1 of kthe coupling network 2|5. In effect, aresistance-capacitance network of very low impedance is connectedbetween the amplier input and ground so that the voltage producedthereacross is at all times sufciently low to permit transmission ofuniform pulses to the coupling network 2|5 regardless of the droppingrate, thus achieving proportionality of the output voltage of thedropping rate meter 13 and the input pulse rate.Y The lead 2 |4 which isconnected to the cathode of triode A of said tube 2|| couples thevoltage developed across the cathode resistor 2|3 to the voltagegenerator 80.

In Fig. 6 said lead 2 |4 supplies a positive pulse of voltage during thefirst interval of operation to a resistor 2|8 in the sawtooth wavegenerator circuit 62 of the voltage generator 80. Said resistor 2|8 isconnected to the control grid of a pentode tube 2| 9. Furtherconnections of said tube 2 I9 are as follows: the cathode is connectedto ground; the screen grid is Vconnected to the Volt direct currentsource through a dropping resistor 22| the plate is connected to the+280 volt direct current source through a dropping resistor 222 and tothe control grid of triode A of a double triode tube'223 through acoupling network 224 comprising a resistor 225 connected in parallelwith a condenser 226. Other connections of triode A of said tube 223 areas follows: the control grid is connected to the 150 volt direct currentsource through a dropping resistor 221 and to the lead |3| through aneon bulb 228 and a resistor 229 to impress on said control grid avoltage of waveform |06 as shown on Fig. 3, the cathode is connected toground, and

the plate is connected to the +280 volt direct current source through adropping resistor 23| and to the plateof a thyratron tube 232 through acoupling network comprising a condenser 233 connected in parallel with aneon bulb 234. Further connections of said thyratron tube 232 are asfollows: the plate is connected to the 150, volt direct current coursethrough a dropping resistor 236,V to a voltage divider, comprising aresistor 231, a potentiometer 238, and a resistor 239 in series, whichis connected to the -150 volt direct current source, to a lead 240, andto a condenser 24|; the control grid is connected to the adjustable armof potentiometer 238 of said voltage divider; the cathode is connectedto said condenser 24|, to the control grid of a pentode tube 242, and tothe' control grid of said tube 2 I9 through a coupling network V243,comprising a resistor 244 connected in parallel with a condenser 245, inseries with a resistor 246. Other time connections of said pentode tube242 are as follows: the cathode is connected to ground, the screen gridis connected to the +150 volt direct current source, and the plate isconnected to the +280 volt direct current source through a droppingresistor 241 and to the control grid of triode B of said tube 21 I.Further connections of triode B of said tube 211 are as follows: theplate is connected to the +280 volt D. C. operating voltage, and thecathode is connected to ground through a biasing resistor 248 and to acoupling network 249 comprising a condenserV 250 connected in parallelwith three series connected neon bulbs, 251, 252 and 253. Said couplingnetwork 249 is connected to the 200 volt direct current source through adropping resistor 254 and to said coupling network 243.

The input lead 240 furnishes a voltage of Waveform 103 to the controlgrid of triode A of a double triode tube 258 in the output circuit 84through a resistor 259. The plate of triode A of said tube 258 has noconnections, and the cathode of this tube is connected to a lead 260which supplies a voltage of waveform 109 as shown on Fig. 3.

The control grid of triode A of said tube 258 is n connected to thecontrol grid of triode A of a double'triode tube 26 I Other connectionsof triode A of said tube 261 include a connection from the plate to the+280 volt direct current source and a connection from the cathode to thecathode of triode B of said tube l261. Further connections of triode Bof said tube 261 include: a connection of the plate to the +280volt'direct current source, a connection of the control grid to ground,and a connection of the cathode to the -150 volt direct current sourcethrough two biasing resistors 262 and 263. Said resistor 262 is alsoconnected to a lead 183 which serves as the output of the voltagegenerator 80 and'supplies a voltage of waveform 1 10 as shown on Fig. 3to other sections of the polaroscope circuit.

In the sawtooth wave generator 82, as described above, the lead 214impresses a voltage proportional to the dropping rate on the controlgrid of the pentode amplier tube 219 which serves as the first stage ofamplification ina four stage negative feedback amplier. 'The rst andsecond stages of amplification, comprising said tube 219 and triode A ofthe double triode tube 223 respectively, 'are conventional and amplifythe input voltage signals. The output voltage of the second amplifierstage is obtained from the plate of triode A of said tube 223 and iscoupled through the condenser '241 to the control grid of the thirdstage of amplification comprising the pentode tube 222. The thyratrontube 2132 is connected in parallel with said condenser 241 in such amanner 'that the tube is normally cut-oi`f and conducts only when thevoltage across said condenser 241 reaches the 'conduction voltage 'ofthe tube. The third stage of 'amplification is coupled in a conventionalmanner to the fourth stage which comprises the triode B ofthe tube 211connected to `operate as a cathode .follower type of amplier. The outputvoltage of said fourth stage of amplification is obtained across thecathode resistor 254 of triode B of said tube 211 and this voltage.being of opposite phase with reference to the input voltage is fed backto the control grid of the first ampliiier tube 219 to oppose the inputvoltage. The Values of the elements in the circuit are such that theoutput voltage of the four stages of amplification isproportional to theinput voltage and therefore proportional to the dropping rate. Thus,vdurmg the first interval ofoperation said condenser` 221 charges at arate proportional'to the drop-v ping rate until the voltage across thecondenser 241 reaches the conduction voltage of said thyratron tube 232,at which time' the tube 232 conducts and rapidly discharges saidcondenser 241 so that the voltage produced has a sawtooth waveform. Thisaction is repeated during the second interval oi operation and anothervoltage of sawtooth waveform `is produced. In the Lthird period ofoperation a positive voltage of rectangular wave Yform 106as shownori-Fig. 3 Vis impressed on the control grid of triodeA lof the tube 223of the second amplifier stage and this voltage acts in opposition to thesignal voltage transmitted from the plate'of the rst amplifier tube 21SsoV that the resulting vvoltage at the condenser 251 is slightlynegative `to prevent the condenser from charging positively and Vthethyratron tube from conducting. Thus, a voltage of waveform 108 asVshown'on Fig. Sis de-y veloped across said condenser 241 during thethree intervals of operations and is transmitted to other parts of thepolaroscope circuit by the lead 240.

Said lead 249 is connected into the output circuit and-supplies `avoltage as related above to the resistor 259. Since said resistor isconnected to 'the control grid of'triode A of'the double triode tube258, the voltage applied is of the waveform 108 as shown on Fig. 3. Theplate of said triode A of the tube 258 is left disconnected while thecathode is connected to the lead 2&0 which applies -a negative voltageof i rectangular waveform 109 as shown on'Fig. 3.

Thus, during the first and third intervals, any positive voltagesappearing at the control grid of triode A of said'tube 25B'are groundedthrough the tube as the cathode is much more negative than the controlgrid by virtue of the negative potential applied. However, in the-seeond pe,- riod 'the voltage impressed on the cathodebf said triode Aof the tube 258 rises to ground potentiai'so that this tube will notconduct and a voltage of vsavvtooth waveform is impressed on the controlgrid "of triode A of the tube 251. Triode A and triode B of said tube261 :are connected as a cathode follower so that thev positive voltageof sawtooth waveform impressed on the control grid of said triode Aduring the second interval is reproduced with the Vsame phaserelationship across the cathode resistor v'263.- The lead 183isconnected in such a manner that'the voltage across said resistor-263-having a Lwaveform 110 as shown on Fig. 3 is transmitted to other'sections of the polaroscope circuit.

InFig. 7 the lead'2'4 lfurnishes a voltage of waveform 108 as shown onFigi?, and is connected toa coupling condenser 264 vin the triggercircuit 92 of the' timer V11). Said Vcouplir-i'g condenser 254 isconnected to the -150 volt direct current source through a droppingresistor 2615, to the control grid of triode Aoi -a double triode 'tube261 through a grid biasing resistor 268,and to the control grid ofVtriode B of `said tube 261 through a grid biasing -resistorvl269-Further connections of triode A of said ftube 261 are: the cathode Visconnected to ground; the-control grid is connected to the `'plate/oftriode B of said tube 261 through a coupling network '21!) comprising acondenser 211 connected in parallel with .a resistor 212'; *theplate isconnected to the +280 vol-t direct current source through a droppingresistor 213, to the control grid of triode 1B Aof said tube `261through a coupling network 211i- .AfL

comprising a condenser 215 connected in parallel with a resistor 216,and to the control grid of triode B of the tube 258. Other connectionsof triode B of said tube 261 include a connection of the plate to the+280 volt direct'current source through a dropping resistor 211 and aconnection of the cathode to ground. Section B of said tube 258 isfurther connected as follows: the plate is connected to the +280 voltdirect current source, the cathode is connected to a lead 218 and toaneon bulb 219. Said neon bulb 219 is connected to the -200 Volt directcurrent source through a dropping resistor 280 and to the plate of diodeA of a double diode tube 28| through a coupling .network 282 comprisinga condenser 283 connected in parallel with a resistor 284. The plate ofdiode A of said tube 28| is connected to the 150 volt direct currentsource through a dropping resistor 285 and to the lead 269 whichsupplies a voltage of waveform |09 as shown on Fig. 3,130 othercomponents of the p-olaroscope. The cathode of diode A of said tube 28|is connected to ground.

Said lead 218 is connected to the control grid of triode A of a doubletriode tube 289 of the trigger circuit 94 through a coupling condenser29|. Triode A of said tube 289 is connected as follows: The control gridis connected to the +150 volt direct current source through a droppingresistor 292 and to the plate of triode B of the same tube through acoupling network 293 comprising a condenser 294 connected in parallelwith a resistor 295; the cathode is connected to ground; the plate isconnected to the +280 Volt direct current source through a droppingresistor 296, to the control grid of triode A of the double triode tube|89,` and to the control grid of triode B of said tube 289 through acoupling network 291 comprising a condenser 298 connected in parallelwith a resistor 299. Further connections of triodeB of said tube 289are: the plate is connected to the +280 Volt direct current sourcethrough a dropping resistor 300; the cathode is connected to ground; andthe control grid is connected to the -150 voltdirect current sourcethrough a dropping resistor 30| and to the lead which supplies anegative pulse of voltage during the rst interval of operation through acoupling condenser 302. The plate of triode A of said tube |89 isconnected to the +280 Volt direct current source and the cathodeisconnected to a neon bulb 303 which is connected to the cathode ofdiode B of the tube 2|8| andA to the lead |3|. The plate of said diode Bof the tube 28| is connected to ground.

The trigger circuit 92, of the timer 90 described above, is connected sothat negative pulses are applied simultaneously to the control grid oftriodes A and B of the double triode tube 261 and cause the tubes toconduct in an alternate manner. The input lead 240 supplies a voltage ofwaveform |08 as shown on Fig. 3 to the differentiator circuit comprisingthe condenser 264 and the resistor 266. Since a differentiator circuitoperates to provide an output voltage which is proportional to the rateof change of the input voltage, the output voltage of saiddifferentiator circuit is a negative pulse of voltage appearing at theend of the rst and second intervals of operation. During the firstinterval triode A of the tube 261 is conducting ther and is reected tomake more current flow4 through triode B, the triode A is soon cut-offoutput voltage of the differentiator comprises negative pulse of voltageat the end of the rst interval of operation and this voltage is appliedVsimultaneously to the control grid of both triode VA and triode B ofsaid tube 261. This negative pulse of voltage at the control grid oftriode B of Asaid tube 261 has no eiect as the control grid is alreadysuiciently negative to hold the tube at cut-off; however, the negativepulse of voltage at the control grid of triode A of this tube 261 startsa cumulative action which almostinstantaneous- 1y causes triode A tocut-off and triode B to conduct heavily. Said cumulative action involvesboth triode A and triode B of said tube 261 and is as follows: thenegative pulse of voltage at the V.control grid of triode A decreasestheeffective voltage and thereby causes the current owing through saidtriode A to decrease; the decrease of current ilowing through saidtriode A lowers the voltage drop across the plate dropping resistor 213and thereby increases the plate voltage; since the plate of triode A iscoupled to the control grid of triode B through the coupling network214, the increase of plate voltage at triode A causes the voltage at thecontrol grid of triode B to increase and therefore current begins to owthrough said triode B; this current flow in said triode B produces avoltage drop through the plate dropping resistor V211 and therebydecreases the voltage at the plate of triode B; said decrease of voltageat the plate of triode B is coupled to the control grid of triode A bymeans of the coupling network 210 so that the voltage at the controlgrid of triode Avis decreased still further; since the voltage at thecontrol grid of triode A yis decreased still furand triode B isconducting heavily. The triode B of said tube 261 continues to conductheavily I and triode A of this same tube 261 remains and triode B ofthis same tube 261 is cut-off at a negative potential. As statedpreviously the cut-off during the second interval until the rate ofchange of the input voltage to the differentiator circuit is sufficientto cause a negative pulse of voltage to appear at the control grid ofthe two triodes. Since a negative pulse of voltage occurs at the end ofthe second interval when the input voltage of sawtooth waveform dropsfrom maximum. positive value to a small negative Value almostinstantaneously, the circuit is triggered, in a manner similar to theaction described above, to the original state wherein triode A of thetube 261 is conductingand triode B of the same tube is cut-off. Theoutput voltage of the trigger circuit is connected from the plate oftriode A of the tube 261 to the control grid of triode B of the tube 258so that said triode B of the tube 258 is cut-olf during therst and thirdintervals of operation when the control grid is sufliciently negativewith respect to the cathode to keep the tube cut-off. During the secondinterval said triode Bof the tube 258 conducts since the potential onthe control grid is raised above the cut-off value. Thus, since thevoltage at the cathode of triode B of the tube 258 varies in phase withthe voltage at the control grid, the voltage at Lsaid cathode isnegative during the first and third intervals while said tube is cut-01Tand approaches a positive value in the second interval. Said resultingrectangular wave of Voltage is transmitted.

by the 1ead'218 to the trigger circuit. of the timer and is connected tothe lead 260 through a low impedance coupling network 282. `The voltageof the lead 260 is by-passed to ground so that the tube conclnbts anytime the cathode .recomesneeatitesrith ressectftaihc platee"fo'omes-more. positive'than-.the cathode.; :Said lead v comprisingresister 306 and apotenicmete i mairteris* connected to the Acontrolvgrid: of. trioldeyA r`of e dcubletriodetube 2308-. brvlieans 0i its, ad-

Tryirciiiti'to-the .control-J. grid bof' triode yAzofcthe f ltbef 2 89iinthe f' trigger .circuit 1 945 .through .a s dir"--'ferentiator.circuitcomprising the condenser29l @and thei-resistonZ-QZiso-that this control :grid-re- =`fthe second intervalvandanegatiuepulses'of vlta-ge1attherendf of.'the-secondfintervah ,Triode fandtriodeB of fthe' tubef289 are interconnected 4f-asi atigger-circuitsoithatzthexflow lof: .currentn ethetubesections .cani be controlled.The `.control figridfof triode B oil-said tube 289 receives aznega--tiv'e'f'pulsefofv voltage lat thefend oi i Ythe :third-in-'Iltervalsfroni the impulsef `generator* by: means.- of

eifopei:ation triode lAof said tube289-is conductaV "ing-heavily while'triode B of4 this: same tube .is cutoli 'Th'eactionof this triggercircuit 94 isQas :1f-follows?v4 at thefstartv of: the" second :intervala ltositive pulse of voltage is impressed .onthe con- -trolfgridottriode'Agbut has noreffect on the-:tubeI flperation-asit' is-'conductingatthistime; a negaftive pulse impressedlonf the `control -grid of.: triode @A `at--the'=startffof.rthe Athird interval causes-thecurrentiiowthrough-the tubeto decrease, which *l decreases the potentialacross: the plate dropping-- 'resistor 236,'andthus increases the fplateVoltage; sincetiie plate 'oftriocle A islconnected tozthe "controlgridfof -triodeB through thecouplingfnetji-'work-l29-1, the-increaseofplate voltage Iat triode r1-A is `applied to=the contro1-gridof Atriode VBythus "-'-raising -the potential of--sthe control grid and'f'ffcausing-fcurrent"to1now through. this `section of Nfthe-"tube 2895;the flow of-current lthrough triode '-ffB l:increases 'the Ivoltageydrop acrosslthe plate fdroppingf resistor 300, thereby decreasingthej-"fplate'voltageof triode B; the decrease of plate foltagerat triodeyB=is transmittedtor the control grid-'of triode A through the =1couplingnetwork "i293, 'thus l'decreasingthe potential of this con-"'trol'fgridy'since'voltage changes inthe tubeele- "*X'nenits aretransmitted--from-triode Arto triode B wcandwiceiversa; and since thevoltage'changes "--transmittedare' cumulative-at the tube elements,vtriode A ie'almost instantaneously cut-oirih and itriode B isconducting heavily. vr",Ilnetrigger-ciri``ct`1it remainsfin'- this stateof operation until the iend"of-"the third interval whenfalfnegative-pulse {fof-voltage is impressed'onthe control grid of tri'odeB of'thetube 289and thev trigger circuit ir/operates' again inaffmanner-similarto that de- -"'Scrib`ed'above= so that triode A isconducting andtriodeBis cut-off. The Voltageat the-plate-of *'htriode fA ofthe' tube289` is connected tothe contr'ol grid of-'trio'de `A ofthe double triodetube 18S """softhat" the' operation ofvthis tubev follows^-the- *platevoltageof triode A`of saidftu'be 289. Thus the output-'voltage of thetrigger'c'ircuit as *ftakenffrom"the'cathode oitriode A of the tube1139fbytheflead vi3! has the rectangular-Waveinstable. element...Othergconnecticns cf saidiirliode A of; tube 308;*areg. the plateisAconnecteclito the JV,e280 froltfI direct current Source :iv ...and thecathode is connected .toile biasineresistslr .39.9411

1 .connected to the .:lvoltdirect.currentsource trol grid oftriodeBfsaid-tube"308 through a abiasing resistor: 313ik Furtherconnetionslof triodev B of'said-tube 3fmy are as follows: .thecathode isconnectedtofercund; thecontrol ,grids is lic-onnected tot|he-l5G Voltdirect current source -ethrough aldropping'resistor 314, vandto a`resistor SI5 .which is connected tothe plate 4,throughl a i couplingnetwork 3;! 6. comprisingl/ acondenser 3 l1 in parallel with two neonbulbs 31.8and`3119l1and further: to the @20,0 volt -.di1ectcurrent'source through audroppingv resistor 32 I and, the plate 1 .isfurthenconnected tothe V-i-Zvolt direc c urrentA supply through4 adropping 4resistor 322y and vto the-control grid ofapentodetube323through 'l a@ coupling network.azicomprisingia ycondenser32 5 in .parallel with; a" resistor 326. .K Sa id.pentode tube323is.'iurtherconnected vas follows.: .,thecon- `trolgrid is. connected,throught@ resistor. `32"'.L to .a resistance voltage 'divider between..the '+150 volt and 150 volt .direct currentzsources coniprising aresistor` 3,28, a .potentiometer .323and a'resistor 33 l-, andfto theplate, througha-resistor 332.; the .cathode isl `-connected` toground;VVV ,the

, screen grid isconnected to; the screenvgrid of andirect current sourcethrough a dropping resistor .lead 338. Saidtube- 333 is connectedinthefollowing manner.: the. -catho,de..is.` connected, to

ground; the control grid is. connectedto1 apoint between .resistors 3Hand 312 inthecathodecir- .cuit-.of triodeelI of said tube 308;, throughacoupling network.:333 comprising a condenser 340 in parallel Witharesistor 34 I, toay pointubetween the potentiometer-32,9-and theresistor 33| ofthe voltage'divider through a-resist0r -342 ,f1-and ifQthe plate ofthis` tube througha resistor 343;.;the

- plate is connected tothe +283 volt direct current source through a.compensating inductor344 and va dropping resistorA 3dS, and` tofa lead346,.

Said leads 333 and .Sare connected to the .vertical deflectionplates,.of acathode ray tube 35i-1- in the cathoderay tube circuit 50 andsupply#la -Voltageiof waveform. i133` asshQWnon Fig.` 3.

- -hehorizontal deflection plates of saidfcathode ray. tube-y 34-.1v.are.asupplieda `AVoltagey ofv Waveform .--I Icy-as I showni-on Fig..3. bysleafs- 34,8. and 55,49.

fVoltages-or the cathode ray tube 341 elements iaresupnlied by .aresista-nceiroltaee divisi@ 9911- nectecl -between,-ftlie.,

1 i sourccfand Iground l rnprising Va ,potentiometer rwoiresisiors..1354 and potnticmeterand 3.51, and afresistorf {Ihe cathode @maidinstable armf .said potentiometer. 35| .which arves. .as fthewintensiiy:GQntrOl; .'QhQ-ifmlmlzgrd isf; connectedsatothefwlQOD Volt f directCliment supply; -the rst acceleratingpanode isconnected to theadjustable arm of said potentiometer 353 which serves as the focusingcontrol; the second accelerating anode and the screen anode areconnected to the +280 volt direct current source.

The input voltage of the balanced amplifier 30 circuit described aboveis transmitted from the output of the negative feedback amplifier l bythe lead |44 and has the wave form l 03 as shown on Fig. 3. Said inputvoltage is impressed on the control grid of triode A of the' doubletriode tube 308, which is connected in the form of a cathode follower,across the resistor 306 and the potentiometer 301. Said potentiometer301 may be adjusted as the Y gain control and determines the verticalspread of the polarogram on the screen of the cathode ray tube 341. TheVoltage developed across the biasing resistor 3| 2 in the cathodecircuit of triode A of the tube 308 is impressed on the control grid oftriode B of this same tube 308 and on the control grid of a pentodeamplifier tube 333. Triode B of said tube 308 is connected into thecircuit to invert the voltage applied at the control grid before thevoltage is amplified by the pentode amplifier tube 323. Said pentodetubes 323 and 333 are connected as conventional wide band amplifiers andfurnish voltages by means of the leads 338 and 346 of like waveform |03,but of opposite phase relationship, to the vertical defiecting platesfor push-pull voltage operation of the cathode ray tube 341. The normalcontrol grid bias of the two amplifier tubes 323 and 333 is supplied bya resistance voltage divider comprising the resistor 328, thepotentiometer 329 and the resistor 33|. Said potentiometer 329 may beadjusted to vary the control grid bias and thereby shift the polarogramalong the vertical axis of the cathode ray tube 341 screen and is knownas the Y position control. The value of the voltage necessary to shiftthe polarogram is small and does notv appreciably affect the gain of thetwo amplifiers.

In the cathode ray tube circuit 50, said leads 338 and 346 furnish avoltage proportional to the current flowing in the dropping mercury cellto the vertical deflecting plates. The leads 348 and 348 furnish avoltage proportional to the voltage applied across said dropping mercurycell 28 as will be described hereinafter. Thus, with these voltagesapplied to the defiecting plates of the cathode ray tube 341, a traceshowing the current-voltage relationship of the dropping mercury cell 28is visually portrayed on the screen of said cathode ray tube 341. Theintensity of the electron beam may be adjusted by varying the potentialapplied at the cathode of the cathode ray tube; that is, by varying theposition of the adjustable element of the potentiometer 35|. The focusof the electron beam on the screen of said cathode ray tube may beadjusted by changing the position of the Variable element of thepotentiometer 353.

In Fig. 9, the lead |83 furnishes a voltage of sawtooth waveform ||0 asshown on Fig. 3 across a voltage divider comprising a resistor 351 and apotentiometer 358. The adjustable arm of said potentiometer 358 isconnected to the control grid of triode A of a double triode tube 359.Other connections to triode A of said tube 359 are as follows: the plateis connected to the +280 volt direct current source; and the cathode isconnected to a biasing resistor 36| in parallel with a by-pass condenser362 which is connected to the -150 volt direct current source through adropping resistor 363, and to the control grid of triode B of said tube359 through a biasing resistor 364. The remaining elements ,of triode VBof said tube 359 are connected as follows: the cathode is connected toground; the control grid is connected to the lead 260, through adropping resistor 360, which supplies a voltage of waveform |09 as shownon Fig. 3, to the +150 volt direct current source through a droppingresistor 367, and to a resistor 368, which is connected to the platethrough a coupling network 369 comprising a condenser 310 in parallelwith two neon bulbs 31| and 312 and further to the 200 volt directcurrent source through a dropping resistor 313; and the plate is furtherconnected to the +280 volt direct current source through a droppingresistor 314 and to the control grid of a pentode tube 315 through acoupling network 316 `comprising a condenser 311 in parallel with aresistor 318. Said pentode tube 315 is further connected in thefollowing manner: the cathode is connected to ground; the control gridis connected, through a resistor 319, to a resistance voltage dividerbetween the volt and 150 volt direct current sources comprising aresistor 38|, a potentiometer 382, and a resistor 383, and to the platethrough a resistor 384; the plate is connected to the +280 volt directcurrent source through a compensating inductor 386 and a droppingresistor 381 and to the lead 348; and the screen grid is connected tothe screen grid of a pentode tube 388 and to the +280 volt directcurrent source through a dropping resistor 389. Other connections ofsaid pentode tube 388 are: the cathode is connected to ground; thecontrol grid is connected to a point between said resistors 36| and 363in the cathode circuit of triode A of said tube 359 through a couplingnetwork 392 comprising a condenser 393 in parallel with a resistor 394,to a point between the potentiometer 382 and a resistor 383 of thevoltage divider through a resistor 395, and to the plate through aresistor 396; the plate is connected to the +280 volt direct currentsupply through a compensating inductor 391 and a dropping resistor 398and to a lead 349.

The reproducing amplifier 40 described in the preceding paragraph issupplied by the lead |83 with a voltage of sawtooth waveform H0 as shownon Fig. '3. Said lead`|83 impresses said voltage of sawtooth waveformacross a resistance voltage divider comprising the resistor 351 and thepotentiometer 358. Said potentiometer may be adjusted as the X gain anddetermines the horizontal spread of the polarogram on the screen of thecathode ray tube 341. This reproducing amplifier 48 operates in a mannersimilar to the balanced amplier 30 described above in that theadjustable element of the potentiometer 358 supplies they input voltageof Vsawtooth waveform to a cathode follower stage comprising the triodeA of the double triode tube 359 and the voltage across the cathoderesistor 363 of said cathode follower stage is amplified through twoparallel channels of conventional wide band amplifier stages comprisingpentode tubes 315 and 388 in opposite phase relation. The phaseinversion is accomplished in one of the channels through triode B ofsaid tube 359. The plate voltage of the two amplifier stages isconnected to the horizontal deflecting plates of the cathode ray tube341 by the two leads 348 and 349. The normal control grid bias of thetwo amplifier stages is supplied by a resistance voltage dividercomprising the resistor 38|, the potentiometer 382 and the resistor 383.Said potentiometer 382 may be adjusted to vary the control grid bias andthereby shift the polarogram along the horizontal axis of the cathoderay tube 3M screen and is known as the X position control. The value ofthe voltage necessary to shift the polarogram is small and does notappreciably affect the gain of the two ampliers. A voltage ofrectangular Waveform |09 as shown on Fig, 3 is applied to the controlgrid of triode B of the tube 359 so that during the iirst and thirdintervals of operation this control grid bias voltage is sufficient tokeep the tube cut-oil and only signal voltages impressed during thesecond interval will be reproduced through the tube. This action duringthe rst and third intervals causes the beam of the cathode ray tube 3&1to be deected ofi the screen of the cathode ray tube 3M so that there isno visible trace on the screen of the cathode ray tube 341. During thesecond interval when the voltage of sawtooth waveform is applied acrossthe dropping mercury cell 29,; the voltage applied by the lead 269 tothe control grid of triode B of the tube 359 is zero and Signal voltagesare thus reproduced through this tube to the cathode ray tube and thetrace is visible on the screen.

The connections and operations of the coinponents of the polaroscopehave been described individually. Now, the starting operation of thepolaroscope as a unit will be disclosed.

The operation of the polaroscope may be initiated by one of severalprocedures, however, the polaroscope is normally started by turning onthe power supply Hill, and then, when said power supply IBG has reacheda steady state of operation, the dropping mercury cell 29 is connectedto the negative feedback amplifier circuit I as shown on Fig` 4. Thevalues of the circuit elements in the timer 99 are such that the outputvoltage of the trigger circuit 92 is negative and the output voltage ofthe trigger circuit 94 is positive, as soon as the operation of thepolaroscope is initiated. Since the output voltage of said triggercircuit 92 is negative and is connected by the lead 260 to severalcomponents of the circuit, the control grid of triode B of the tube 359in the reproducing ampliiier l0 becomes negative to deect the electronbeam of the cathode ray tube 341 oi the screen, the cathode of triode Aof the double triode tube 258 becomes negative to block any signal fromreaching the output of the output circuit Si! of the voltage generator8l). Aliso, since the output voltage of said trigger circuit 9d ispositive and is connected by the lead |3| to several components of thecircuit, the control grid of the pentode tube ||2 in the negativefeedback amplifier |8 is positive toimpress a positive voltage acrossthe dropping mercury cell 20, the plate of the tube |72 in the dropdetector it circuit is positive to allow signal voltages at the controlgrid to be reected to the impulse generator 16, and the control grid oftriode A of the tube 223 in the voltage generator 80 is positive toblock any negative pulses of voltage received from the plate of the tube2| 9.

With the above conditions existing, the iirst mercury drop falling fromthe tip of the capillary electrode |61 causes the resistance of thedropping mercury cell 29 to increase sharply, thereby decreasing theamount of current iiowing through said cell'ZB, and reecting to theoutput of the negative feedback amplier it an instantaneous voltagedecrease. Since the voltage output of said negative feedback amplifierl0 is connected, by means of the lead |44, to the derivator 'i2 of theinitiator 7D, a negative pulse of 12 in response to said instantaneousvoltage decrease, and thusly, at the time the iirst mercury drop fallsfrom the tip of the capillary electrode |61. Said negative pulse ofvoltage is coupled from the derivator l2 to the drop detector 'ill bythe lead lll; thus, since said drop detector 14 is sensitive, a positivepulse of voltage appears at'the plate of the pentode tube |12. The lead|16 applies said positive pulse ci voltage at the plate of said pentodetube |12 in said drop detector 'It to the impulse generator 'i6 whichfurnishes a negative pulse of voltage of a standard value to the triggercircuit 9d of the timer S0, by means of the lead Rill, and to thedropping rate meter 7S by means of the lead Zilli. Said negative pulseof voltage impressed by said lead 28| on the trigger circuit 9d tripsthe operation of this circuit so that the output of voltage dropsinstantaneously from a positive value of voltage to zero. With thevoltage output of said trigger circuit 94 at zero value, the voltageacross the dropping mercury cell 2i] is zero and any further mercurydrops falling from the dropping mercury electrode |51 will have noeffect on the circuit operation; also, since the voltage applied to thecontrol grid of the tube 223 in the voltage generator 4becomes zero, thesawtooth wave generator 82 becomes sensitive for the generation ofvoltages.

As stated above, said impulse generator 'i6 furnishes a negative pulseof voltage to the dropping rate meter 18. Since said dropping rate meter'I8 is connected to average the input pulses of voltage, the outputvoltage is proportional to the rate at which the input pulses of voltageoccur, thus, the ouput voltage is proportional to the dropping rate ofthe mercury drops. Obviously, the output voltage of said dropping ratemeter 'i8 will not be proportional to the adjusted dropping rate of thedropping mercury cell 2Q and will not reach a steady value until ten tolifteen drops have formed and fallen from the tip of the capillaryelectrode |51.

The voltage output of said dropping rate meter I9 is applied to thesawtooth Wave generator 82 of the voltage generator S and charges thecondenser 24| until the voltage across said condenser 24| reaches theconduction voltage of the thyratron tube 232. When the voltage charge ofsaid condenser 24| reaches the conduction voltage or said thyratron tube232, this tube rires, and in so doing discharges the condenser 26| veryrapidly, thus forming a voltage wave across said condenser 2M whichrises from zero to a maximum value over a period of time and thenreturns to zero in an extremely short time, in other words, a sawtoothwave of voltage. The output voltage of said sawtooth Wave generator istransmitted to the trigger circuit si of the timer Sil and to the outputcircuit 8B or" said voltage generator Se by the lead 2st. At the timesaid saw-tooth wave of voltage changes from maximum positive value tozero, a negative pulse of voltage is impressed on the control grids ofthe doubleY triode tube Ztl, and the trigger circuit 92 is tripped sothat its output voltage rises from a negative Value to zero. Since theoutput voltage of said trigger circuit 92 is connected to the cathode ofthe tube 25S in the output circuit 84 and to the control grid of triodeB of the tube 359 in the reproducing ainplier d, said output circuitbecomes sensitive to pass voltages from the sawtooth wave generator 82and the-electron beam of the cathvoltage is formed at the output of saidderivator u ode ray tube 341 is returned to the screen to 21 trace thecurrent-voltage relation `of the electrolyte in the dropping mercurycell 20.

Thus, it is seen that the circuit is now ready to complete the cycle ofoperation and provide a visual trace of the current-voltage relation ofthe electrolyte being tested in the dropping mercury cell 20. This naloperation occurs when the condenser 241 in the sawtooth wave generator82 charges for the second time at a rate proportional to the rate atwhich mercury drops fall in the dropping mercury cell 22 and dischargeswhen the conduction voltage of the thyratron tube 232 is reached, thatis, when a second voltage of sawtooth waveform is produced by thesawtooth wave generator 82. Said second voltage of sawtooth Waveform istransmitted from the sawtooth wave generator 82 to the trigger circuit92 by the lead 24% and to the output circuit 84 by the same lead. Saidoutput circuit 84 reproduces and transmits said second voltage ofsawtooth waveform by the lead 183 to a resistance voltage divider in thedrop detector 14 and to the input circuit of the reproducing amplier 4t.The value of the second voltage of sawtooth waveform impressed acrossthe dropping mercury cell 2E), through the negative feedback amplier 'bymeans of the lead H6, is controllable by the potentiometer ISI, which ispart of said resistance voltage divider in said drop detector 14. Thus,the second voltage of sawtooth Waveform with the desired magnitude isimpressed across the electrolyte solution in the dropping mercury cell2D and voltage changes at the output of the negative feedback amplifierl0, in response to current changes in said cell 29, are transmitted tothe balanced amplier 3i).

The voltag-e ofsawtooth waveform applied to the reproducing amplifier 40is the same as that applied to the dropping mercury cell 20 and isamplified through two channels of amplification, one of which isopposite in phase to the other, and the resultant voltages are thenimpressed on the horizontal deiiecting plates of the cathode ray tube341 for push-pull operation. The input voltage of the balanced amplifier36 which is proportional to the current iiovving through the electrolyteof the dropping mercury cell 20 is ampliiied in a similar manner as inthe reproducing amplifier 40 and is then impressed on the verticaldelecting plates of the cathode ray tube 341 for push-pull operation.With these voltages applied to the derlecting plates of the cathode rayturbe 341, the electron beam traces the current-voltage characteristicof the electrolyte under analysis. However, as has been pointed outVpreviously the voltage output of the dropping rate meter 18 does notreach maximum value until ten or fifteen drops have fallen, so thattraces appearing on the screen of the cathode ray tube 341 will not beaccurate until this number f drops have fallen.

At the termination of the second voltage of sawtooth Waveform asimpressed on the trigger circuit S2 of the timer 90, a negative pulseoccurs to trip this circuit and the output voltage decreases fromzerot-oa negative value. Since the output voltage of said triggercircuit 92 is connected to the input of the trigger circuit l94 of thetimer 90, a negative pulse occurs when said trigger circuit S2 trips andcauses the output voltage of said trigger circuit 94 to change from zeroto a positive value. Thus, the voltage have returned to the conditionsexisting prior to the time the first mercury drop fell from the tip ofthe capillary electrode |61 of the dropping mercury cell developed.

20 and the circuit is operative to repeat the cycle as soon as anothermercury drop falls,

c Consider now a cycle of operation after ten or fteen mercury dropshave fallen and beginning at an instant shortly before another mercurydrop falls from the tip of the capillary tube |61 of the droppingmercury cell 20, that is, an instant prior to the end of the thirdinterval of a normal cycle of operation as dened earlier in thisdisclos-ure.

At this moment the output voltage of the trigger circuit A92 is negativeand the output voltage of the trigger circuit 34 is positive. Sincethese output voltages exist, the drop detector 14 is operative, thevoltage generato-r is inoperative, a small positive voltage is presentacross the dropping mercury cell 20 and at the output of the negativefeedback amplier I0, and the electron beam is deliected off the screenof the cathode ray tube `341. As the drop continues to enlarge, theresistance of the dropping mercury cell 2@ gradually decreases yand thevoltage appearing at the output of the negative feedback amplier I@increases slowly.

When the drop breaks from th-e tip of the kcapillary tube l 61, theresistance of the dropping mercury cell 20 suddenly increases so thatthe voltage appearing at the output of the negative feedback amplifier Iand at the input of the derivator 12 in the initiator 10 suddenlydecreases, causing a positive pulse of voltage to be impressed on thedrop detector 14. Since at this time the drop detector 14 is sensitiveby virtue of the positive potential impress-ed on the plate of thepentode tube I 12 by the timer 90, a negative pulse of voltage isproduced at the output of said drop detector 14, and this negativepuls-e of voltage is applied to the impulse generator 1E. Thecorresponding standard pulse of voltage produced by the impulsegenerator 16 is applied to the timer to trip the trigger circuit 94,causing the output voltage of this trigger circuit 94 to change from apositive value to zero, thereby ending the third interval and startingthe first interval of operation.

The change of the output voltage of the trigger circuit 94 to zero valuerenders the sawtooth wave generator 82 Vof the voltage generator 80operative to produce sawtooth Waves of voltage, reduces the outputvoltage of the negative feedback amplifier 0 to zero, and renders thedrop detector '14 insensitive to changes of voltage at its input. Assoon as the sawtooth Wave generator is made operative, the condenser 24!charges at a rate proportional to the rate at which pulses of voltageappear at the output olf the impulse generator 1S and thus at the inputof the dropping rate meter 18. Said `condenser 24| charges in a linearmanner until the conduction voltage of the thyratron tube 232 isreached, at which voltage said tube con-ducts and rapidly dischargessaid condenser 24|, so that a voltage of sawtooth waveform is Thisvoltage of sawtooth Waveform is applied to the output circuit 84, whichat this mom-ent is inoperative for transferring any voltage to the inputof the negative feedback amplier I0 by virtue of the fact that theoutput voltage of the trigger circuit 92 is still negative.

When the thyratron tube 232 conducts, discharging the condenser 24|, theiirst interval ends and the second interval is initiated. The decreaseof voltage resulting from the discharge of the condenser 24| causes anegative pulse to be applied to the trigger circuit 92, thus trippingthis circuit so that the output voltage increases

